February 2005

Fee Fee Creek, located in Maryland Heights, Missouri, a suburb of St. Louis, is a tributary to the Creve Coeur Creek, which in turn flows into the Missouri River. As Maryland Heights developed in the 1960s and 1970s, a mix of commercial and residential development occurred upstream and along the channel bank. As a result, the creek experienced an increase in runoff and velocity of water. Through the years, homeowners began dumping grass clippings and other debris down Fee Fee Creek's banks, killing vegetation that had held soil in place.

Fast-forward to 2001, and the once-attractive, meandering stream had changed dramatically. Because of the increase in stream flow, the creek began to undergo entrenchment, a process by which the stream bottom drops, which caused the banks to slide into the stream. The entrenchment of Fee Fee Creek was so advanced that residents were losing their backyards; some fences were ready to tumble into the water. Left unchecked, the creek threatened to claim sheds and swimming pools.

The City of Maryland Heights stepped in to stabilize a 1,900-foot section of Fee Fee Creek. The City hired Woolpert LLP, a consulting firm that provides engineering and environmental planning and design, to study Fee Fee Creek's problems and recommend a sustainable stream design solution. Woolpert assembled a team of surveyors, geotechnical engineers, hydraulic engineers, and environmental scientists to perform the project, which included:

Topographic and boundary surveys.

Hydrologic and hydraulic modeling.

Biostabilization design.

Plans and specifications preparation.

Cost estimating.

Easement plat preparation.

Bid services.

Technical support during construction.

At the center of Woolpert's recommendations was the use of certain in-stream and on-bank design techniques—including the J-Hook Weir, Newbury Riffle Pool, wrapped earth, and root wads. These techniques have been used in other regions of the United States but were relatively new to the St. Louis region. They are part of a sustainable stream design movement that takes a natural and holistic approach to stream stabilization.

Although the City of Maryland Heights is considered progressive when it comes to stormwater management, some City officials and local homeowners were still a little skeptical of the techniques that Woolpert was recommending. Convincing stakeholders that sustainable stream design is as effective as traditional stream improvement methods—not to mention healthier for water quality and wildlife—was part of the educational process that included public presentations describing the process and benefits.

"We're taking a different approach to creek stabilization," said L.G. Loos, P.E., Assistant Director of Public Works for the City of Maryland Heights. "We're looking at Fee Fee as an overall unit—as an entire ecosystem—instead of doing spot fixes. We're learning what caused problems to form in the first place and remedying them with sustainable solutions."

OverviewFee Fee Creek was identified by the City of Maryland Heights' stormwater management committee as highly eroded and therefore eligible for capital improvement. The $600,000 stabilization project would be paid for in part by a State of Missouri stormwater grant. Woolpert LLP was hired by the City of Maryland Heights for its engineering and environmental expertise and knowledge of sustainable stream design solutions that had been implemented in such states as Ohio, Kentucky and North Carolina.

The first step was to walk Fee Fee Creek to take samples, to evaluate existing conditions, and to determine the root causes of the degradation. What was found was not only a highly entrenched stream but also evidence of man-made carelessness, including discarded car parts and tires, old washing machines, concrete rubble, and rotting yard waste. A number of large diameter trees had fallen into the creek, while others were about to.

Woolpert's next step was to conduct a topographic and boundary survey in which the locations of trees, homes, fences, stream banks, and property lines were identified. Woolpert further defined the stream's existing characteristics by computer-modeling Fee Fee Creek using the hydraulic software HEC-RAS. The results established baseline hydraulic conditions for use in determining the impact of the proposed construction.

Based on the field investigation, various surveys, computer modeling, and the geotechnical investigation, it was determined that a combination of natural on-bank and in-stream design solutions would be used to stabilize Fee Fee Creek. The creek was again modeled using HEC-RAS to verify that there would be no rise in the 100-year water surface elevation (as defined by FEMA) as a result of the proposed stream improvements. Construction drawings and specifications were prepared to the same level of detail as traditional engineering projects and issued for bid.

On-bank solutionsThe stream banks and riparian zones were fortified using several techniques that worked in concert with each other. One technique was the rip rap toe, a commonly used method that stabilizes the base of a bank. In the case of Fee Fee Creek, large rip rap stones were installed along the lowest three feet of eroded bank areas.

In one area of Fee Fee Creek, a more radical approach, the rock buttress, was needed to shore up a 22-foot-high bank that had no room to flatten the existing 1H:1V failing bank slope. Stones ranging from six inches to two feet in diameter (five pounds to 650 pounds) were placed on the face of the 1:1 slope. Once a depth of five feet of rock had been achieved, soil was compacted on top. Coir fabric and willow live stakes were then installed.

In the area of a particularly sharp bend, the rip rap toe was supplemented with a technique known as a root wad. This technique consists of recycling large trees (18 inches to 24 inches in diameter) that have fallen over because of erosion.

The tree trunk is cut 10 feet to 12 feet above the root ball, and the end is sharpened in the shape of a pencil tip. Then, the pointed end is embedded eight feet into the existing earth, leaving the root ball exposed along the bank and facing slightly upstream to absorb scour energy, thus reducing the impact of shear stress on the bend. A series of root wads is set in place with the root balls overlapping each other while large stone is placed around the exposed trunks. Depending on the species, the root balls can last up to 25 years while providing scour protection and aquatic habitat.

"It's like a natural 'armor' that protects the bank at sharp turns," explained Joseph Krypciak, P.E., a senior engineer with the City of Maryland Heights. "We felt it was an odd technique at first, but we believe it's based on sound principles and will be effective at Fee Fee Creek." A bank treatment known as wrapped earth was used to compliment the root wads.

The wrapped-earth technique consists of wrapping coir fabric—a woven coconut fiber mesh—around compacted earth lifts and placing willow branches between each lift. Wrapping the earth in this way enables rebuilding and revegetating banks at a somewhat steeper slope than simply compacting the earth. In areas of milder slopes, coir fabric was laid directly on top of the earth and live willow stakes were driven through the fabric and into the bank.

The live branches and live stakes are installed during the dormant period of the growing season (late winter to early spring). The stakes and branches are about 48 inches in length and have a diameter of 1/4 inch to 1/2 inch. They consist of a mix of Buttonbush, Streamco Willow, Banker's Willow, and Redosier Dogwood.

In addition to willow plantings, native shrubs, grasses and wildflowers—those with deep root structures and that thrive in the shade—will be planted along Fee Fee's banks. A variety of trees will also be planted along the banks to help shade the water, reduce the temperature and promote aquatic habitat.

"Revegetating the banks of Fee Fee Creek is the common 'theme' or technique throughout the design," Krypciak said. "We're following an approach that is supported by the U.S. Army Corps of Engineers—to use natural methods which not only stabilize the creek but also support aquatic life. Just a few years ago, we might have considered Fee Fee solely for its drainage function and lined this channel with concrete—and that's what a lot of people are used to seeing. But residents are really pleased with these more natural techniques."

In-stream solutionsA total of six J-Hook Weirs, so called because the placement of rocks involved resembles a "J," will be developed around bends in Fee Fee Creek. The technique was pioneered by Dave Rosgen, a geomorphologist and founder of Wildland Hydrology based in Pagosa Springs, Colorado. It has been used for about a decade throughout the United States but still is still gaining acceptance in the St. Louis region.

The rocks are placed without gaps between them nearer the bank (to slow the water and direct it toward the center of the stream) and with gaps between them nearer the center and end of the J-Hook (where the swirl of water is more beneficial, creating deeper, oxygenated pools for aquatic life). Rocks should be square; their size depends on the size and velocity of the stream. At Fee Fee Creek, the size of rocks will vary from 2-1/2 feet to 3-1/2 feet across, weighing from 1,000 pounds to 4,000 pounds.

The Newbury Riffle Pool—also gaining popularity in the St. Louis region—was chosen as another way to slow the velocity of water as well as to improve water quality by aerating the water with riffles and providing deeper pools for aquatic life. A total of 11 Newbury Riffle Pools are being installed at Fee Fee Creek.

Created by Robert Newbury of Newbury Hydraulics in British Columbia, Canada, the technique is based on the principle that riffles and pools can be created to mimic naturally occurring riffle-pool complexes. Just like their naturally occurring counterparts, the man-made riffles at Fee Fee Creek are being strategically placed to create upstream pools through the bends.

To create this system, the riffle crest first is built across the stream using large-diameter boulders. At Fee Fee Creek, stones from 2-1/2 feet to 3-1/2 feet in diameter (1,000 pounds to 4,000 pounds) were used to create the crest, which spans the width of the stream and embeds into the bank. The goal is to set the crest stones at the proper elevation to create the desired pool elevation upstream of the crest.

SummaryThe natural on-bank and in-stream techniques that were chosen to help stabilize Fee Fee Creek not only will address erosion but also will become an attractive and integral part of the stream's ecosystem designed to promote aquatic and wildlife habitat for years to come. By assembling a team of qualified engineering and environmental professionals, Woolpert was able to provide the City of Maryland Heights with a natural, effective, and long-term method to address the stream degradation problems at Fee Fee Creek.